Embodiments of the invention generally relate to a power distribution network and, more particularly, relate to a system and method for controlling operations of components in a power distribution network that include variable or fluctuating power generators such as, for example, a photovoltaic (PV) power generator or a wind turbine generator.
Electrical power transmission and distribution networks typically include centralized power generation plants, transmission lines, distribution lines, transformers, and other devices that facilitate electric power transmission and delivery. After electric power is generated in central generation plants, the power is typically transmitted for extended distances through high voltage transmission lines to sub-transmission/distribution substations. From the substations, power is then transmitted through a distribution network to end customers.
Some known distribution networks also include distributed power generators that may be susceptible to fluctuations caused by acts of nature, such as photovoltaic (PV) power generators or wind turbines. PV generators, for example, convert solar radiation into direct current electricity and contribute that electricity to the distribution network for local use. However, output from PV generators fluctuates with cloud cover. On cloudy days, PV generators may contribute relatively little electricity to the distribution network, where on sunny days PV generators may contribute a substantial amount of electricity to the network. Further, as clouds move through the vicinity, PV generator output may spike and dip multiple times throughout a day, presenting wide variations of overall power output contributed to the network, and relatively quick fluctuations between low and high output.
In order to control certain aspects of the distribution network, (e.g., maintaining the voltage within nominal voltage bounds), electrical power distribution networks sometimes include additional control devices such as capacitor banks and voltage regulators. These devices execute control actions that, for example, switch between operating and non-operating states, or switch in steps to alter one or more attributes such as voltage within the distribution network. These changes may help, for example, to mitigate the voltage excursions beyond the nominal voltage bounds. In some known systems without fluctuating generators such as PV, controllers are able to adequately manage voltage within given limits because shifts due to changes in network conditions are generally more predictable or less dramatic. However, the presence of fluctuating generators on the distribution network, such as PV, may lead to excessive switching operations as the control devices chase net load variability on the downstream network. Excessive switching of the additional control devices leads to reduced life spans of the devices and increased maintenance costs.